A Jazzmaster coil is very thin and squat, thinner even than a P90.They still have magnetic poles like a Strat single coil but the coil shape the string sees underneath it is much wider, more like a P90.
A P90 differs in so much as it has 2 humbucker sized magnets facing in towards pole screws-this alone provides a lot more power and combined with the squat,fat coil of a P90, a chunkier tone too.
We don't do Jazzmasters simply because there's not much call for them, we do rewind them alot though for customers likewise Jags too.